The present invention relates generally to orthotics and more specifically to a knee brace for providing support for the knee of a person.
Knee braces for providing support for the knee of a person are well known in the art. Such braces generally include a tibial shell which is constructed so as to be closely configured to the shape of the lower leg and a femoral shell which is constructed so as to be closely configured to the shape of the thigh area of the leg. The two shells are secured to their respective areas on the leg and are interconnected by some type of mechanism so as to pivot relative to each other as the knee is bent. The mechanism is usually a pair of hinge joints, one on each side of the knee brace, with the tibial shell usually being attached to the lower part of each one of the two knee joints and the femoral shell usually being attached to the upper part of each one of the two hinge joints.
Knee braces are often utilized by people who have suffered a knee injury and require some means of protection against further aggravation of the knee during rehabilitation. A knee brace can limit the amount of damage to an injured knee by providing the patient with adequate knee stabilization and control. Stabilization and control is achieved in such a manner as to permit the patient relative freedom in the normal use of the knee joint while, at the same time, permitting control over the joint so as to optimize healing.
In addition, knee braces are often employed by a person having previously suffered a knee injury who wishes to actively participate in strenuous and demanding physical activity. In such cases where the person seeks knee support in furtherance of activities involving heavy running or sprinting, it is extremely advantageous to design a knee brace which most accurately simulates the true motions of the anatomical knee joint. Where a knee brace fails to adequately correspond to the actual motion of the human knee joint, the knee brace will tend to ride down the leg of the person after limited use and will generate more force through the knee capsule, thereby exposing the patient to increased risk of further injury to the knee.
In the past, a number of attempts have been made to create a knee brace which moves with a simple gliding motion and which accurately parallels the intricate movement of the knee joint. However, the motion of the human knee joint in its stages of flexion and extension are quite complex; therefore, attempting to create a knee brace which can properly duplicate the motion of a knee joint has been met with substantial difficulty. First, the movements of flexion and extension in the knee joint differ from those in a typical hinged joint, such as the elbow or hip. The axis around which motion takes place in the knee joint is not fixed, but rather the axis shifts forward during extension, as the gliding movement is superimposed on the rolling motion and the axis shifts backwards during flexion.
In U.S. Pat. No. 4,699,129 to G. V. Aaserude et al, which issued on Oct. 13, 1987, there is disclosed a polycentric variable axis pivotal hinge system especially designed and adaptable to follow the complex movement of the knee when incorporated in a knee brace, the hinge having an upper and a lower extension overlying a central linking member and pivotally connected thereto wherein each extension moves in a relative angular motion determined by the coaction of a guide pin follower slidably and pivotally interacting with slots in the angular terminal portions of the extensions and the guide pin follower moving in a vertical slot in the central member; with provision for motion limiting stops. Although generally useful, it should be noted that a polycentric variable axis hinge such as shown in U.S. Pat. No. 4,699,129 has certain drawbacks. For instance, when incorporated in a knee brace, the aforementioned hinge fails to provide for rotational movement of the knee joint. In particular as the knee goes into flexion, the tibia will rotate about a vertical axis through the knee joint. Similarly, when the knee is straightened, the knee joint will generally rotate in the Opposite direction, usually along the same path the knee joint moved in the stages of flexion. Generally, the rotation of the knee joint occurs during the first 25 degrees of flexion; however, the pattern of rotation and anterior-posterior flexion in the knee joint can vary considerably between any two people. Therefore, it is desirable that any knee joint which is implemented in a knee brace be able to accommodate the different paths of rotation as well as anterior-posterior movement of the tibia relative to the femur in knee joints of a broad spectrum of people. The above-described hinge fails to accommodate the natural tendency for the leg to rotate, and therefore will disrupt the knee joint's natural motion. As a consequence, this hinge will inadequately represent the motion of the knee joint and consequently, the drawbacks enumerated above will potentially develop.
In U.S Pat. No. 4,986,264 to M. E. Miller, there is disclosed a knee brace having an anterior tibial shell and an anterior femoral shell which are closely configured to the shape of the lower leg and thigh respectively and which are joined by a frame in the form of a pair of polycentric hinge joints. Each one of the joints includes an upper bar and a lower bar, the two bars being pivotally interconnected. The anterior tibial shell and the anterior femoral shell are both pivotally mounted on the upper bars of the polycentric hinge joints, the anterior femoral shell being mounted above the anterior tibial shell. Because the anterior tibial shell is mounted on the upper bars of the two joints when the knee brace is mounted on the leg of a person and the knee is bent the anterior tibial shell will move downward and inward against the tibia so as to counteract forward directed forces applied to the tibia and thereby provide additional support for the knee. The knee brace also includes a pair of derotation cuffs removably mounted on the femoral and tibial shells for internally rotating the femur and externally rotating the tibia, respectively.
In U.S. Pat. No. 4,733,656 to S. Marquette there is disclosed a knee brace having an anterior tibial shell and a posterior femoral shell which are closely configured to the shape of the lower and thigh areas of the leg, the two shells being joined by a closed support band system which is constructed to closely tract knee flexion. The band system includes upper vertical uprights and lower vertical uprights which are pivotally interconnected to each other. The femoral shell is attached to the upper vertical uprights while the tibial shell is attached to the lower vertical uprights. The brace also has anteriorly extending tabs positioned between the patella and the femoral epicondyles. The combination of two shells, the band system and the two tabs provides anterior-posterior, medial-lateral and rotary stability.
In U.S. Pat. No. 4,773,404 to J. H. Townsend there is disclosed an appliance for controlling an unstable knee joint in the sagittal, coronal and transverse planes, comprising femoral and tibial cuffs joined by femoral and tibial links which are interconnected to provide a novel mechanical joint wherein camming slots are formed in one of the links with cams disposed on the other link, the slots comprising straight segments and arcuate segments so as to provide approximately 8 millimeters of sliding movement between the femur and the tibia, followed by relative rotation about the center of radius of the femoral condyle as the leg is flexed. The tibial cuff is conformed about the bony prominence or shin or the tibia to inhibit rotation of the leg beneath the knee within the brace itself.
Other patents of interest include U.S. Pat. No. 4,732,143 to J. Kausek et al, U.S. Pat. No. 4,599,998 to J. D. Castillo, U.S. Pat. No. 4,393,542 to G. Martinez, U.S. Pat. No. 4,387,709 to C. A. Shen, and U.S. Pat. No. 4,337,764 to M. Lerman.